The present invention relates to the reaction of chlorotrifluoroethylene, hereinafter designated as "CTFE", with bisfluoroxydifluoromethane, hereinafter designated as "BDM", to produce highly fluorinated telomers. The telomers thus formed hve properties which distinguish them from other CTFE telomers and make them commercially attractive products. Such properties include superior solvent characteristics which are useful in formulating non-flammable hydraulic fluids.
Various methods of preparing telomers from CTFE are known in the prior art and have been practiced commercially for many years.
An article by William T. Miller, Jr. et al in Industrial and Engineering Chemistry, pages 333-337 (1947), entitled "Low Polymers of Chlorotrifluoroethylene", describes a process for producing low molecular weight polymers of CTFE by carrying out the polymerization in a solution of chloroform using benzoyl peroxides as polymerization promoters. Other solvents disclosed in the reference as being useful for this purpose include carbon tetrachloride and tetrachloroethylene. The solution is heated in a pressure vessel for 13/4 hours at 100.degree. C., and the unreacted CTFE monomer and chloroform are removed by distillation, leaving a "crude" telomer of general formula CHCl.sub.2 (CF.sub.2 CClF).sub.n Cl, which can be further heated and distilled to yield products ranging from a light oil to a semi-solid wax or grease. In this formula, n designates the chain length (the number of repeating units in the telomer chain), and is in the range of 1 to 20.
A more recent development in this field is described in a series of articles by Y. Pietrasanta et al entitled "Telomerization by Redox Catalysis" appearing in the European Polymer Journal, Vol. 12 (1976). This technology involves the reaction of a chlorinated telogen, such as carbon tetrachloride, with CTFE in the presence of benzoin and a suitable redox catalyst, such as ferric chloride hexahydrate (FeCl.sub.3.6H.sub.2 O). The telomerization reaction is suitably carried out in acetonitrile which is a common solvent for the reactants and catalysts. The telomerization reaction can be illustrated as follows, wherein n is as defined above: ##STR1##
The telomers produced according to the above-described process have end groups containing chlorine atoms. When used in a particular application, especially high temperature or corrosive applications, the chlorine atoms can be hydrolyzed, which may result in cleavage of the telomer and a loss of physical properties of the fluid. In order to prevent such a condition, the end groups are stabilized by fluorinating the telomer to replace some or all of the chlorine atoms with fluorine. The fluorine atoms form a stronger bond with carbon and are less prone to cleavage. This results in a fluid which has superior performance over a wider range of operating conditions.
Fluorination of the telomer is accomplished by reaction with a suitable fluorinating gent, such as chlorine trifluoride or hydrogen fluoride. However, fluorination involves an additional process step which increases processing costs. It would be desirable to reduce the amount of fluorination required or eliminate this procedure in its entirety. It would also be desirable to develop superior telomers having improved physical characteristics, such as better solvent properties. These are the primary objectives of the present invention.